Resistive coating for a capillary

Abstract

A coated capillary tube having a tunable resistance in an ion transfer device, including an inlet end in communication with an atmospheric-pressure ion source, an outlet end in communication with a vacuum region of a mass spectrometer, a body elongated along an axis from the inlet end to the outlet end, and an inside surface defining a bore having an inner diameter is disclosed. The coated capillary tube also includes a resistive coating on the inside surface of the capillary tube, in which the resistive coating includes at least one layer comprising oxides or nitrides of a metal and discrete metal particles of a different metal embedded therein.

We claim: 
     
         1 . A coated capillary tube having a tunable resistance coating in an ion transfer device, comprising:
 an inlet end in communication with an atmospheric-pressure ion source;   an outlet end in communication with a vacuum region of a mass spectrometer;   a body elongated along an axis from the inlet end to the outlet end;   an inside surface defining a bore having an inner diameter; and   a resistive coating on the inside surface of the capillary tube, the resistive coating comprising:
 at least one layer comprising metal oxides or metal nitrides, and discrete metal particles of a different metal or metal oxide embedded therein. 
   
     
     
         2 . The capillary tube of  claim 1 , wherein the metal oxides include a metal oxide of Al2O3, TiO2, Y2O3, Ta2O5, HfO2, ZrO2, SiO2 or a combination thereof. 
     
     
         3 . The capillary tube of  claim 1 , wherein the resistive coating further comprises a metal or metal oxide of Pt, Ru, W, Mo, or a combination thereof. 
     
     
         4 . The capillary tube of  claim 1 , wherein the resistive coating includes a total end-to-end resistance of from about 100 MOhm to about 50 GOhm. 
     
     
         5 . The capillary tube of  claim 1 , wherein the resistive coating includes a total temperature coefficient of resistance of from about −2%/° C. to about −1%/° C. 
     
     
         6 . The capillary tube of  claim 1 , wherein a length of the capillary tube is from about 75 mm to about 200 mm; an outer diameter of the capillary tube is from about 5 mm to about 10 mm;
 and an inner diameter of the capillary tube is from about 0.1 mm to about 2.0 mm.   
     
     
         7 . The capillary tube of  claim 1 , wherein the bore includes a sheet resistance that decreases in resistance on one or both ends of the capillary tube. 
     
     
         8 . The capillary tube of  claim 1 , wherein the resistive coating further comprises a base layer, a final layer, or both. 
     
     
         9 . The capillary tube of  claim 8 , wherein the final layer includes a thickness that is greater than a diameter of the discrete metal particles. 
     
     
         10 . The capillary tube of  claim 8 , wherein the base layer includes a thickness that is greater than a diameter of the discrete metal particles. 
     
     
         11 . The capillary tube of  claim 8 , wherein the base layer, the final layer, or both comprise oxides or nitrides of a metal. 
     
     
         12 . The capillary tube of  claim 8 , wherein the base layer comprises a plurality of sublayers of metal oxides, metal nitrides, or a combination thereof;
 wherein the at least one layer including discrete metal particles comprises a plurality of sublayers including a plurality of discrete metal particles; and   wherein the final layer comprises a plurality of sublayers of metal oxides, metal nitrides, or a combination thereof.   
     
     
         13 . The capillary tube of  claim 1 , wherein the at least one layer comprises a plurality of alternating layers including a plurality of layers including discrete metal particles and a plurality of layers including oxides or nitrides of the metal. 
     
     
         14 . The capillary tube of  claim 1 , wherein the at least one layer includes a thickness of from about 1 nm to about 800 nm; and wherein the resistive coating includes a thickness of from about 0.5 nm to about 1 μm. 
     
     
         15 . A resistive coating for a substrate, the resistive coating comprising:
 a base layer comprising SiO2, TiO2, Y2O3, Ta2O5, HfO2, Al2O3, ZrO2, AlN, ZrN, or a combination thereof,   a plurality of discrete metal or metal oxide particles layers comprising Ru, W, Mo, Pt, or a combination thereof; and   a plurality of covering layers comprising SiO2, TiO2, Y2O3, Ta2O5, HfO2, Al2O3, ZrO2, AlN, ZrN, or a combination thereof,   wherein the plurality of discrete metal or metal oxide particles layers and the plurality of covering layers are alternatingly arranged to create a mixture of discrete metal particles embedded in the plurality of covering layers.   
     
     
         16 . The resistive coating of  claim 15 , wherein one of the plurality of covering layers is a final layer, and the final layer includes a thickness greater than a diameter of the discrete metal particles in each of the plurality of discrete metal or metal oxide particles layers. 
     
     
         17 . The resistive coating of  claim 15 , wherein the plurality of covering layers has a thickness that is less than or equal to a diameter of the discrete metal particles in each of the plurality of discrete metal or metal oxide particles layers. 
     
     
         18 . The resistive coating of  claim 15 , wherein the base layer comprises a plurality of sublayers, and
 wherein each of the plurality of covering layers comprises a plurality of sublayers.   
     
     
         19 . A method of coating an inside surface of a capillary tube in an ion transfer device, comprising steps of:
 (a) performing ALD of metal oxides or metals onto or within the capillary tube comprising:
 (A) introducing one or both aluminum or zirconium precursors followed by purging with an inert gas; 
 (B) pulsing a first oxygen containing compound to react with the aluminum or the zirconium precursors, followed by purging with an inert gas, to create a metal oxide layer; 
 (C) optionally conducting a first number of sub-cycles of deposition of the metal oxide layer to produce a plurality of metal oxide layers; 
 (D) introducing ruthenium, tungsten, molybdenum, platinum, or a combination precursor followed by purging with an inert gas; 
 (E) pulsing a second oxygen containing compound followed by purging with an inert gas, thereby performing ALD deposition of a second layer at a second deposition temperature; 
 (F) optionally conducting a second number of sub-cycles of deposition of the second layer to produce one of a second plurality of layers; and 
 (G) repeating step (A) through (F) for a plurality of cycles to produce a resistive coating on the tube; and 
   (b) removing the coating from outside surface of the capillary tube.   
     
     
         20 . The method of  claim 19 , further comprises annealing the capillary tube including the resistive coating at a predetermined temperature; and further comprises oxidation step or a plasma treatment step of the capillary tube including the resistive coating.